The present invention relates to a method of and an apparatus for automatically coating a workpiece, and more particularly to a method of and an apparatus for automatically coating a workpiece selectively with a plurality of coating materials which can be ejected respectively from a plurality of nozzles directed toward the workpiece and mounted on movable units that can travel along tracks over the workpiece, so that the workpiece can efficiently be coated with the coating materials irrespective of the directions in which the workpiece is transferred into and out of the coating area.
Automotive parts such as an engine hood, a trunk lid, a roof, a door, for example, are coated along their perpheral edges with any of various coating materials such as a highly viscous sealing agent and an adhesive to make the perpheral edges resistant to rust and improve their mechanical strength or rigidity. These coating materials are selected to meet the intended functions of the workpieces to be coated. Generally, a plurality of coating materials are successively coated on a single workpiece.
FIG. 1 of the accompanying drawings illustrates a typical workpiece to be coated, i.e., the reverse side of an automotive engine hood 2. The engine hood 2 has peripheral edges 4 to be held against an automotive body (not shown), the peripheral edges 4 being coated with an adhesive to keep their mechanical strength or rigidity or render them rust-resistant. Various portions 6 of the reverse side of the engine hood 2 are coated with a mastic sealer of high shock absorbing capability for absorbing the vibration of reinforcing members attached to the reverse side of the engine hood 2.
These peripheral edges and portions are conventionally been coated by an automatic coating apparatus having a nozzle for ejecting a coating material. One such automatic coating apparatus is disclosed in Japanese Laid-Open Patent Publication No. 59(1984)-12778. The disclosed automatic coating apparatus comprises an articulated robot having a nozzle for ejecting a coating material and an arm having on its end a gripper which grips the nozzle, the arm being controlled to move the gripper to a desired position.
In operation, the gripper which grips the nozzle is moved by the arm over a workpiece, while the coating material is being ejected from the nozzle to coat the workpiece.
When a different coating material is to be coated on the workpiece, the nozzle is moved by the arm to a replacement position after the preceding coating process, and then is detached from the gripper. A nozzle for ejecting the next desired coating material is now mounted on the gripper, and thereafter is moved by the arm to a desired position over the wrokpiece, followed by a next coating process.
However, each time coating materials are to be changed, the arm must be moved to the replacement position for replacing the nozzle on the gripper. Since the coating operation of the conventional coating apparatus is interrupted during each process of a nozzle replacement operation, the efficiency of the coating operation is quite low. Other problems associated with the prior coating apparatus concern the positioning of the robot on a floor surface. This arrangement imposes limitations on the direction in which workpieces to be coated can be delivered into and out of the coating apparatus, and the robot takes up a relatively large space in the factory.
U.S. Pat. No. 4,564,410 issued Jan. 14, 1986 to Clitheros et al. discloses an adhesive application apparatus for coating an adhesive on an automotive window frame. The adhesive application apparatus has an adhesive-ejecting nozzle movable along guide rails arranged in X and Y directions, the nozzle being also movable in a Z direction. The nozzle can therefore apply an adhesive to a workpiece irrespective of the directions in which the workpiece is transferred into and out of the adhesive application apparatus.
The above prior adhesive application apparatus is however disadvantageous in that since only the single nozzle is attached, different adhesives cannot be changed quickly.
It is a general object of the present invention to provide a method of and an apparatus for automatically coating a workpiece with coating materials that can be ejected respectively from a plurality of nozzles which are displaceable so as to be directed toward the workpiece, the nozzles being selectively operable to coat a desired coating material on the workpiece for meeting a particular subsequent process to be effected on the workpiece, so that the workpiece can highly efficiently be coated in a small space with coating materials that can easily be changed, irrespective of the directions in which the workpiece is transferred into and out of the coating area.
Another object of the present invention is to provide a method of automatically coating a workpiece, comprising the steps of positioning a first nozzle of a first nozzle device closely to the workpiece; displacing the first nozzle device with respect to the workpiece while ejecting a first coating material from the first nozzle toward the workpiece; after the first coating material has been coated on the workpiece, moving the first nozzle device away from the workpiece; positioning a second nozzle of a second nozzle device closely to the workpiece; displacing the second nozzle device with respect to the workpiece while ejecting a second coating material from the second nozzle toward the workpiece; and after the second coating material has been coated on the workpiece, returning the first and second nozzle devices in unison back to respective original positions thereof.
Still another object of the present invention is to provide an apparatus for automatically coating a workpiece, comprising at least one first track; at least one Y-axis mobile body movable on and along the first track; at least one second track mounted on the Y-axis mobile body and extending substantially perpendicularly to the first track; at least one X-axis mobile body movable on and along the second track; at least one third track mounted on the X-axis mobile body and extending substantially perpendicularly to the first and second tracks; at least one Z-axis mobile body movable on and along the third track; and a plurality of nozzle devices mounted on the Z-axis mobile body and displaceable so as to be directed toward the workpiece.
A still further object of the present invention is to provide an apparatus for automatically coating a workpiece, including four X-axis mobile bodies, four Y-axis mobile bodies, four Z-axis mobile bodies, the X-axis, Y-axis, and Z-axis mobile bodies being arranged in confronting pairs, and a pair of nozzle devices mounted on each of the Z-axis mobile bodies.
Yet another object of the present invention is to provide an apparatus for automatically coating a workpiece, wherein one of the nozzle devices is displaceable with respect to the other nozzle device, the nozzle devices having respective nozzles for ejecting different coating materials.
Yet still another object of the present invention is to provide an apparatus for automatically coating a workpiece, wherein the nozzle devices have respective nozzles extending parallel to the Z-axis mobile body.
A yet still further object of the present invention is to provide an apparatus for automatically coating a workpiece, wherein the nozzle devices have respective nozzles inclined to the direction of travel of the Z-axis mobile body and angularly displaced in close relationship to each other.
Still another object of the present invention is to provide an apparatus for automatically coating a workpiece, wherein the nozzle devices can freely be inclined to the Z-axis mobile body.
Still another object of the present invention is to provide an apparatus for automatically coating a workpiece, wherein the different coating materials are a mastic sealer and an adhesive, respectively.
A still further object of the present invention is to provide an apparatus for automatically coating a workpiece, wherein the workpiece is an automotive engine hood, the mastic sealer and the adhesive being applied to prescribed portions of the automotive engine hood.
A yet still further object of the present invention is to provide an apparatus for automatically coating a workpiece, wherein the X-axis, Y-axis, and Z-axis mobile bodies include respective servomotors for moving the X-axis, Y-axis, and Z-axis mobile bodies along the first, second, and third tracks, respectively.
A still further object of the present invention is to provide an apparatus for automatically coating a workpiece, including a cylinder mechanism for moving the nozzle devices with respect to each of the Z-axis mobile bodies.
A yet still further object of the present invention is to provide an apparatus for automatically coating a workpiece, wherein each of the nozzle devices comprises a cylinder mechanism, a valve openable and closable by the mechanism, a nozzle openable and closable by the valve, and means for delivering a coating material to the nozzle via the valve, whereby the amount of the coating material ejected from the nozzle can be regulated by operating the cylinder mechanism to adjust the opening of the valve.
The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.